China, People’s Republic

The use of so-called “green” hydrogen for decarbonisation of the energy and propulsion sectors has attracted considerable attention over the last couple of decades. Although advancements are achieved hydrogen still presents some constraints when used directly in power systems such as gas turbines. Therefore another vector such as ammonia can serve as a chemical to transport and distribute green hydrogen whilst its use in gas turbines can limit combustion reactivity compared to hydrogen for better operability. However pure ammonia on its own shows slow complex reaction kinetics which requires its doping by more reactive molecules thus ensuring greater flame stability. It is expected that in forthcoming years ammonia will replace natural gas (with ~ 90% methane in volume) in power and heat production units thus making the co-firing of ammonia/methane a clear path towards replacement of CH4 as fossil fuel. Hydrogen can be obtained from the precracking of ammonia thus denoting a clear path towards decarbonisation by the use of ammonia/hydrogen blends. Therefore ammonia/methane/hydrogen might be co-fired at some stage in current combustion units hence requiring a more intrinsic analysis of the stability emissions and flame features that these ternary blends produce. In return this will ensure that transition from natural gas to renewable energy generated e-fuels such as so-called “green” hydrogen and ammonia is accomplished with minor detrimentals towards equipment and processes. For this reason this work presents the analysis of combustion properties of ammonia/methane/hydrogen blends at different concentrations. A generic tangential swirl burner was employed at constant power and various equivalence ratios. Emissions OH*/NH*/NH2*/CH* chemiluminescence operability maps and spectral signatures were obtained and are discussed. The extinction behaviour has also been investigated for strained laminar premixed flames. Overall the change from fossils to e-fuels is led by the shift in reactivity of radicals such as OH CH CN and NH2 with an increase of emissions under low and high ammonia content. Simultaneously hydrogen addition improves operability when injected up to 30% (vol) an amount at which the hydrogen starts governing the reactivity of the blends. Extinction strain rates confirm phenomena found in the experiments with high ammonia blends showing large discrepancies between values at different hydrogen contents. Finally a 20/55/25% (vol) methane/ammonia/hydrogen blend seems to be the most promising at high equivalence ratios (1.2) with no apparent flashback low emissions and moderate formation of NH2/OH radicals for good operability.

Hydrogen is considered a secondary source of energy commonly referred to as an energy carrier. It has the highest energy content when compared to other common fuels by weight having great potential for further development. Hydrogen can be produced from various domestic resources but based on the fossil resource conditions in China coal-based hydrogen energy is considered to be the most valuable because it is not only an effective way to develop clean energy but also a proactive exploration of the clean usage of traditional coal resources. In this article the sorption-enhanced water–gas shift technology in the coal-to-hydrogen section and the hydrogen-storage and transport technology with liquid aromatics are introduced and basic mechanisms technical advantages latest progress and future R&D focuses of hydrogen-production and storage processes are listed and discussed. As a conclusion after considering the development frame and the business characteristics of CHN Energy Group a conceptual architecture for developing coal-based hydrogen energy and the corresponding supply chain is proposed.

Energy–structure–function (ESF) maps can aid the targeted discovery of porous molecular crystals by predicting the stable crystalline arrangements along with their functions of interest. Here we compute ESF maps for a series of rigid molecules that comprise either a triptycene or a spiro-biphenyl core functionalized with six different hydrogen-bonding moieties. We show that the positioning of the hydrogen-bonding sites as well as their number has a profound influence on the shape of the resulting ESF maps revealing promising structure–function spaces for future experiments. We also demonstrate a simple and general approach to representing and inspecting the high-dimensional data of an ESF map enabling an efficient navigation of the ESF data to identify ‘landmark’ structures that are energetically favourable or functionally interesting. This is a step toward the automated analysis of ESF maps an important goal for closed-loop autonomous searches for molecular crystals with useful functions.

The cost reduction of hydrogen refueling stations (HRSs) is very important for the popularization of hydrogen vehicles. This paper proposes an optimized operation algorithm based on hydrogen energy demand estimation for on-site hydrogen refueling stations. Firstly the user’s hydrogen demand was estimated based on the simulation of their hydrogenation behavior. Secondly mixed integer linear programming method was used to optimize the operation of the hydrogen refueling station to minimize the unit hydrogen energy cost by using the peak–valley difference of the electricity price. We then used three typical scenario cases to evaluate the optimized operation method. The results show that the optimized operation method proposed in this paper can effectively reduce the rated configuration of electrolyzer and storage tank for HRS and can significantly reduce the unit hydrogen energy cost considering the construction cost compared with the traditional method. Therefore the optimization operation method of a local hydrogen production and hydrogen refueling station proposed in this paper can reduce the cost of a hydrogen refueling station and accelerate the popularization of hydrogen energy vehicles. Finally the scope of application of the proposed optimization method and the influence of the variation of the electricity price curve and the unit cost of the electrolyzer are discussed.

Recent studies of J.H. Song et al. and S.Y. Yang et al. have been concentrated on mitigation measures against hydrogen risk. The authors have proposed installation of quenching meshes between compartments or around the essential equipment in order to contain hydrogen flames. Preliminary tests were conducted which demonstrated the possibility of flame extinction using metallic meshes of specific size.<br/>Considerable amount of numerical and theoretical work on flame quenching phenomenon has been performed in the second half of the last century and several techniques and models have been proposed to predict the quenching phenomenon of the laminar flame system. Most of these models appreciated the importance of heat loss to the surroundings as a primary cause of extinguishment in particular the heat transfer by conduction to the containing wall. The supporting simulations predict flame-quenching structure either between parallel plates (quenching distance) or inside a tube of a certain diameter (quenching diameter).<br/>In the present study the flame quenching is investigated assuming the laminar hydrogen flame propagating towards a quenching mesh using two-dimensional configuration and the earlier developed models. It is shown that due to a heat loss to a metallic grid the flame can be quenched numerically.

In this paper the deflagration region and characteristics of the hydrogen flow which was generated by high-pressure hydrogen discharge from storage vessels were studied. A 3-D analytic model is established based on the species transfer model and the SST k −ω turbulence model. The established model is applied to the research of the flow characteristics of the hydrogen under-expanded jet under different filling pressures of 30 MPa 35 MPa and 40 MPa respectively. The evolution process of hydrogen combustible cloud is analyzed under the filling pressure of 30 MPa. It is revealed that a supersonic jet is formed after the high-pressure hydrogen discharge outlet In the vicinity of the Mach disk the hydrogen jet velocity and temperature reach the maximum values and the variation of filling pressure has little effect on the peak values of the hydrogen jet flow velocity and temperature during the considered pressure range. In the rear of the Mach disk the variation rates of the hydrogen flow velocity and temperature are in inversely proportional to the hydrogen filling pressure. At the preliminary stage the discharged hydrogen is apple-shaped which expands along the radial and then the axial growth rate of the hydrogen cloud increases with the passage of time.

The present review focuses on the production of renewable hydrogen through the catalytic steam reforming of bio-oil the liquid product of the fast pyrolysis of biomass. Although in theory the process is capable of producing high yields of hydrogen in practice certain technological issues require radical improvements before its commercialization. Herein we illustrate the fundamental knowledge behind the technology of the steam reforming of bio-oil and critically discuss the major factors influencing the reforming process such as the feedstock composition the reactor design the reaction temperature and pressure the steam to carbon ratio and the hour space velocity. We also emphasize the latest research for the best suited reforming catalysts among the specific groups of noble metal transition metal bimetallic and perovskite type catalysts. The effect of the catalyst preparation method and the technological obstacle of catalytic deactivation due to coke deposition metal sintering metal oxidation and sulfur poisoning are addressed. Finally various novel modified steam reforming techniques which are under development are discussed such as the in-line two-stage pyrolysis and steam reforming the sorption enhanced steam reforming (SESR) and the chemical looping steam reforming (CLSR). Moreover we argue that while the majority of research studies examine hydrogen generation using different model compounds much work must be done to optimally treat the raw or aqueous bio-oil mixtures for efficient practical use. Moreover further research is also required on the reaction mechanisms and kinetics of the process as these have not yet been fully understood.

Operating chemical looping process at mid-temperatures (550-750 oC) presents exciting potential for the stable production of hydrogen. However the reactivity of oxygen carriers is compromised by the detrimental effect of the relatively low temperatures on the redox kinetics. Although the reactivity at mid-temperature can be improved by the addition of noble metals the high cost of these noble metal containing materials significantly hindered their scalable application. In the current work we propose to incorporate earth-abundant metals into the iron-based spinel for hydrogen production in a chemical looping scheme at mid-temperatures. Mn0.2Co0.4Fe2.4O4 shows a high hydrogen production rate at the average rate of ∼0.62 mmol.g-1.min-1 and a hydrogen yield of ∼9.29 mmol.g-1 with satisfactory stability over 20 cycles at 550 oC. The mechanism studies manifest that the enhanced hydrogen production performance is a result of the improved oxygen-ion conductivity to enhance reduction reaction and high reactivity of reduced samples with steam. The performance of the oxygen carriers in this work is comparable to those noble-metal containing materials enabling their potential for industrial applications.

Today in order to reduce the increase of the carbon dioxide emissions a large number of renewable energy resources (RES) are already implemented. Considering both the intermittency and uncertainty of the RES the energy storage system (ESS) is still needed for balancing and stabilizing the power system. Among different existing categories of ESS the hydrogen storage systems (HSS) have the highest energy density and are crucial for the RES integration. In addition RES are located in faraway regions and are often transmitted to the terminal consumption center through HVDC (high voltage direct current) due to its lower power loss. In this paper we present a power supply system that achieves low-carbon emissions through combined HSS and HVDC technology. First the combined HSS and the HVDC model are established. Secondly the rule-based strategy for operating the HSS microgrid is presented. Then an operating strategy for a typical network i.e. the pure RES generation station-HVDC transmission-microgrids is demonstrated. Finally the best sizing capacities for all components are found by the genetic algorithm. The results prove the efficiency of the presented sizing approach for a pure RES electric system.

Hydrotreatment is an efficient method for pyrolytic oil upgrading; however the trade-off between the operational cost on hydrogen consumption and process profit remains the major challenge for the process designs. In this study an integrated process of steam methane reforming and pyrolytic oil hydrotreating with gas separation system was proposed conceptually. The integrated process utilized steam methane reformer to produce raw syngas without further water–gas-shifting; with the aid of a membrane unit the hydrogen concentration in the syngas was adjusted which substituted the water–gas-shift reactor and improved the performance of hydrotreater on both conversion and hydrogen consumption. A simulation framework for unit operations was developed for process designs through which the dissipated flow in the packed-bed reactor along with membrane gas separation unit were modelled and calculated in the commercial process simulator. The evaluation results showed that the proposed process could achieve 63.7% conversion with 2.0 wt% hydrogen consumption; the evaluations of economics showed that the proposed process could achieve 70% higher net profit compared to the conventional plant indicating the potentials of the integrated pyrolytic oil upgrading process.